I am actually prone to getting really stressed out when my dad gets my dd all worked up, too! However, I have figured out that, for me, there is an interesting reason. I realize that I want my kids on their best behavior when my parents are around, and that my dad is the very one undermining it! LOL. So, ironically, I'm here trying to be sure that they see what great kids we have, and my dad is busy bonding with one of them in the best way he knows how - by getting her to laugh hysterically and be silly. So our plans are incompatible...I realize it's my place to let it happen, and that after my dad has the girls all tired out from the laughing fits, he's happy, they're tired, and it's over.

So for me, the need for me to demonstrate how well-behaved my children are has to come second to my dad's need to make the girls laugh. It's annoying, but it means more to the two of them than it does to me, really. (Your situation could be very different than mine, but I thought I'd throw this out there, anyways.)